A duty list or back rest, possibly (6)
I believe the answer is:
roster
'a duty list' is the definition.
(I've seen this before)
'or back rest possibly' is the wordplay.
'back' says the letters should be written in reverse.
'possibly' indicates an anagram.
'or' written backwards gives 'ro'.
'rest' is an anagram of 'ster'.
'ro'+'ster'='ROSTER'
(Other definitions for roster that I've seen before include "Duty list for sorter" , "List of people's turn of duties" , "Roll" , "Work rota" , "Work list" .)